Multi-faceted Odor Control Planning for Primary Clarifiers (Primary Treatment Process) at Orange County Sanitation District

The Orange County Sanitation District (OCSD) has embarked on a primary clarifier improvement project at its Plant No. 2 facility in Huntington Beach, CA, and effective odor control is a critical component of the project.The OCSD focus on odor management is not new – the facility’s existing 14 clarifiers were fitted 30 years ago with geodesic domes exhausted to two odor treatment complexes. The North Scrubber Complex includes 7 chemical scrubbers and 1 biotrickling filter serving ten primary clarifiers (B and C-Sides), while the South Scrubber Complex includes 4 chemical scrubbers to treat A-Side primary clarifier exhausts. Although the existing system has performed well, the deterioration of aging equipment was a concern, and the primary clarifier upgrade project provided the opportunity to develop a new odor control strategy reflecting evolutions in both cover designs and treatment technologies.A number of overarching objectives defined the project direction, including: meet air permit limits; meet OCSD Strategic Plan goals for offsite impacts (level of service, LOS); provide cost-effective and efficient treatment.The development of new odor control facilities to meet these objectives was complicated by a number of key considerations, including the impact of cover design on operations and exhaust volumes, and the integration of findings from concurrent odor planning efforts.The specific efforts to integrate these factors into an overall decision matrix for the primary treatment project, as well as the recommendations based on the matrix, are the focus of this paper. The approach developed and implemented through this project can serve as a model for utilities facing complicated odor control planning.